For a variety of reasons, therapeutic access to internal cavities of animals, including humans, has been desirable. Herein the term "therapeutic access" will generally be understood to refer to access to the cavity from a remote location, for any of a variety of reasons. For example, the access may be desired in order to introduce therapeutic material into the cavity; in order to remove material from the cavity; and, in order to obtain access to the cavity with mechanical means such as an orthoscopic filament or laser surgery tool. The term "therapeutic access" is intended to include within its meaning access to treat conditions, study conditions, inhibit the onset of physical problems, etc.
There are a wide variety of reasons why access has been desirable, in both human and veterinary medicine. Herein the description will primarily focus on treatments of humans, and the focus of attention will be on joint cavities. Further, conditions of particular interest to the techniques and apparatus described herein are arthritic conditions; however it will be understood that: many of the methods and apparatus described herein may be applied to a wide variety of animals and not just humans; some of the techniques may be utilized for access to cavities other than joint cavities; and, some of the treatment methods described herein may be utilized for therapy other than treatment of arthritic conditions.
Again, a particular area in which the methods and apparatus described herein may be of use, is in the treatment of arthritis. More than 37 million individuals in the United States suffer from the broad category of joint diseases known collectively as arthritis. Among the more common of these conditions are: osteoarthritis, which is prevalent among elderly; and, rheumatoid arthritis, which tends to occur in relatively young men and women. When the pain associated with the conditions cannot be controlled by conservative treatments methods, and/or when function cannot be readily restored, joint replacement is often the presently prescribed treatment method. Approximately 120,000 hip replacements and 70,000 knee replacements are performed each year in the United States.
While joint replacement operations are generally successful for short term relief, loosening of implants and erosion of articulating surfaces pose problems over the long-term. As a result there have been ongoing efforts to improve joint prostheses. However, it is also desirable to develop treatment methodologies that avoid joint replacement or at least postpone its necessity.
Research has indicated that access to synovial fluid of a diseased joint could be a key factor in the development of new treatment methodologies. In particular, the nature of the synovial fluid has been linked to joint disease. A study of changes in the synovial fluid could provide information useful in long-term diagnoses and treatment and access to a joint for direct application of drugs and/or lubricants therein can lead to more effective modes of treatment for arthritic disease.
Cuevas et al., Biochem. Biophys. Res. Comm., 156, 611 (1988), incorporated herein by reference, reported that administration of fibroblast growth factor directly into injured joints of rabbits for 20 days promoted repair of the damaged cartilage; while no evidence of damage repair was seen in control animals which received intra-articular saline infusions. Such studies support the contention that access to synovial fluid may be of considerable therapeutic value.
A typical conventional means of orthopedic joint access for fluid drainage and acute drug therapy has been by percutaneous hypodermic needle insertion. Studies during which artificial synovial fluid has been injected as an experimental treatment include the reports found in: Leardini et al., Clinical Trials Journals, Vol. 24, p. 341 (1987); Namiki et al., International Journal of Clinical Pharmacology, Theory and Toxicology, Vol. 20, p 501 (1982); Grecomoro et al., Phramatherapeutica, Vol. 5., p. 137 (1987); and, Bragantini et al., Clinical Trials Journal, Vol. 25, p. 333 (1987). The previous four recited articles are incorporated herein by reference. In general, the articles report that one to three intra-articular injections per week of 20-40 mg (milligrams) of hyaluronic acid temporally relieved arthritis pain in some patients. However, two of the studies (Namikini et al. and Leardini et al.) report that the injections either produced pain lasting a few hours (3.3-4.7% incidence rate) or swelling which lasted a few days (1.0-2.5 % incidence rate).
Besides the incidence of pain (and/or swelling) associated with treatment through use of hypodermic needles to provide percutaneous insertion, other potential problems and limitations are presented by this conventional technique. Examples of these are briefly discussed herein. The list is not intended to be considered as exhaustive.
If percutaneous hypodermic injection is to be utilized, then therapy extending over a substantial period of time would require subjecting the patient to a plurality of painful injections. This not only increases pain and discomfort to the patient, but also requires the patient to frequently return for treatment to a medical facility, increasing cost and inconvenience.
Another problem with this method of therapy is that treatment on a continuous basis, i.e. through continuous infusion, is not readily feasible. Further, the size of bolus which may be given in any given treatment will be severely limited by the size of the cavity and/or patient comfort.
Also, each injection may need to be precisely located, for maximum therapeutic effect. This may be difficult to achieve. The needle injection itself may cause damage, or provide a site of infection. For example, if the joint of concern is the knee joint, the cavity (or fluid containing capsule) is defined by bone structure and membrane. Generally, needle insertion would require piercing of the membrane. Thus, damage to the integrity of the capsule is involved, and infection may set in. The problem is exacerbated should a plurality of injections be necessary.
The studies of the four references discussed above were carried out on knee joints. Treatment of hip, wrist and finger joints would typically involve more technically difficult percutaneous needle puncture (in the case of the hip) or likely cause unacceptable trauma (in the case of the smaller wrist joint and tiny finger joints).
What has generally been needed has been a more convenient and effective method for obtaining therapeutic access to an internal cavity such as a joint cavity. Apparatus for conducting such methods have also been needed.